Intelligent matching - The algorithms in Geotag automatically match GPS data to your photos. For photos taken when your GPS didn't have a signal you can let Geotag make a guess based on the closest available GPS information.

Fine tune location using Google Maps - You can show a photo's location in your web browser using Google Maps. The map contains a marker you can drag on the map to change the location associated with a photo. The location the GPS records for your photo is the location where you took the

I don't have a gps unit myself, but this program makes adding location information to photographs extremely easy.
Integrated location search with Google maps and the ability to add co-ordinates to a selection of photographs at once make this utility exceptionally easy to use.